1. Field of the Invention
The invention relates to a test liquid used to simulate the effects of a coolant condensate on an electrical power station component in the event of an accident involving an escape of coolant condensate.
It is known from Published French Patent Application 2,225,819, corresponding to U.S. Pat. No. 3,821,640, to use a test liquid to wet an insulated cable in order to check its insulation.
In the case of a coolant loss accident (CL accident), major amounts of steam are generally produced. The condensate that then occurs wets numerous components, including the energy generation and distribution and control systems. That creates a moist film, which becomes conductive from contaminants on the component surface. If one of those components is impaired in its function or destroyed by the condensate that wets it, for instance because its cables, distributors and leadthroughs are poorly insulated, the result can be that the provisions necessary to control the accident are made more difficult. Moreover, not only the coolant system but also the components damaged by the condensate will then have to be repaired.
In order to avoid such damage, all of the components of a power station that could become wetted with condensate in the event of a CL accident are built in such a way that they are not impaired in their function by being wetted under accident conditions, for instance by being encapsulated, potted, or equipped with long creep paths (so-called coolant loss resistance).
Since as a rule insulation materials age, and thus the coolant loss resistance can drop over the service life of a component from external factors and even the operation of the component itself, the coolant loss resistance of affected components should be checked regularly by suitable processes. One such process is disclosed in the commonly assigned U.S. Pat. No. 5,773,982 entitled: "Process for Checking the Efficiency of an Electric Power Station Component.", which was filed simultaneously with the instant application.
In particular, that process enables such testing without having to remove the component. Thus connections or distributors, for instance, can be tested in the operationally ready state without destruction or dismantling and the test can even be performed during ongoing operation. the test process in accordance with the commonly assigned U.S. Pat. No. 5,773,982 entitled: "Process for Checking the Efficiency of an Electric Power Station Component.", which was filed simultaneously with the instant application, provides for simulation of the wetting by condensate in the case of the coolant loss accident by applying a test liquid of defined conductivity that provides good wetting, in order to then measure the insulation resistance as a value for the functioning of the component. The surface is subsequently dried again. The surface may preferably be rinsed before drying with a residue-free, removable rinsing medium.
If a crack occurs in the coolant system, especially for instance, in a nuclear reactor cooled with light water, then because of the high pressure at the elevated operating temperature, the water escapes into other parts of the power station in which electrical components are located. This water condenses on the various components, and while it largely drops off them (especially when their surface is very clean), nevertheless if dust has deposited on them after relatively long periods of operation, it mixes with that dirt. The result is that on the magnet drives for the control rods, the open-loop and closed-loop control devices and signal systems, a moist film of dirt at approximately 160.degree. C. forms, which can cause short circuits in the power supply, incorrect signals or missing signals and other defects that impair the function of those devices. The vulnerability to malfunction is further increased by the pressure of the coolant vapor.
The process detects the danger of such functional disturbances in good time to enable taking suitable countermeasures (such as replacing the threatened components).